There are hybrid vehicles known from Japanese Patent Application Laid-open Nos. 5-340241 and 56-101012, wherein a heat energy of an exhaust gas from an internal combustion engine is converted into a mechanical energy in a Rankine cycle system, and a driving force for the vehicle is assisted by the mechanical energy, or a generator is driven by the mechanical energy to provide an electric power.
There is also a conventionally known hybrid vehicle including an internal combustion engine and an electric generator motor, wherein a driving force from the internal combustion engine is assisted by a driving force from the electric generator motor during acceleration and cruising of the vehicle, and a battery is charged by a regenerative electric power of electric generator motor during deceleration of the vehicle.
It should be noted here that when a Rankine cycle system is mounted on a vehicle, a heat energy of an exhaust gas from an internal combustion engine can be recovered during acceleration and cruising of the vehicle, but there is a problem that a kinetic energy of a vehicle body cannot be recovered in the Rankine cycle system during deceleration of the vehicle. In a hybrid vehicle, a kinetic energy of a vehicle body can be recovered as a regenerative electric power of an electric generator motor during deceleration of the vehicle, but there is also a problem that a heat energy of an exhaust gas from an internal combustion engine cannot be recovered during acceleration and cruising of the vehicle.